Your boat should be documented with the coast guard.... which also means that if the fed government decides they need to use it, they can... but it also makes your boat U.S. property when you go to other countries.... in that regard... the don't tell is the best solution to any defensive weapons these days....

In order of importance....

12 gage pump... 3" mag. OO buck

either an AK or AR.... full metal jacket

handgun...

Don't forget that 12 gage flare gun

I would devise a place for storage that will require some serious searching to find them